1. Field of the Invention
The invention relates to recording and reading digital data on a moving magnetic medium particularly with respect to a ring-type magnetic head therefor.
2. Description of the Prior Art
Ring-type heads are ubiquiously utilized in the moving magnetic medium storage technology for recording and reading information in both the longitudinal mode and in the perpendicular mode. Although achieving high density recording on the magnetic surfaces is desirable, such high density recording results in a compromise in the optimum gap length of the ring head. Reading back information which has been recorded at high linear densities, for example, in excess of 50,000 flux changes per inch, requires a very short gap in the ring head. Ring heads, however, having adequately short gaps for reading at high densities are unable to adequately overwrite previously recorded information. In order to read such high density recorded information, gap lengths on the order of ten microinches are required. Such a gap length is not fully effective in properly recording or overwriting in either the longitudinal mode on, for example, a longitudinal thin-film medium or in the perpendicular mode on the somewhat thicker perpendicularly oriented magnetic medium.
One solution to the problem is the utilization of two heads, one for reading and the other for writing. The read head utilizes a short gap and the write head a longer gap which may be approximately two to four times longer than the reading gap. The utilization of two heads undesirably increases the system cost, complexity and space requirements. The ring-type head is particularly adaptable to the conventional Winchester-type arrangement where the head assembly flies aerodynamically over a magnetic disk.
In a somewhat unrelated context, U.S. Pat. No. 4,317,148, issued Feb. 23, 1982 to Chao S. Chi, discloses a transducer particularly adapted for perpendicular magnetic recording. The transducer of said U.S. Pat. No. 4,317,148 utilizes a sub-core with an auxiliary winding for controllably providing a ring-type gap for reading and single pole performance for recording. The construction of the transducer of said U.S. Pat. No. 4,317,148 is relatively complex and expensive, requires auxiliary windings and additional electrical excitation and control.